Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/10—Beam splitting or combining systems
  • G02B27/1006—Beam splitting or combining systems for splitting or combining different wavelengths
  • G02B27/102—Beam splitting or combining systems for splitting or combining different wavelengths for generating a colour image from monochromatic image signal sources
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V13/00—Producing particular characteristics or distribution of the light emitted by means of a combination of elements specified in two or more of main groups F21V1/00 - F21V11/00
  • F21V13/12—Combinations of only three kinds of elements
  • F21V13/14—Combinations of only three kinds of elements the elements being filters or photoluminescent elements, reflectors and refractors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
  • F21V9/30—Elements containing photoluminescent material distinct from or spaced from the light source
  • F21V9/32—Elements containing photoluminescent material distinct from or spaced from the light source characterised by the arrangement of the photoluminescent material
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
  • F21V9/40—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters with provision for controlling spectral properties, e.g. colour, or intensity
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
  • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Definitions

• This invention relates to solid-state light emitting devices with photoluminescence wavelength conversion and in particular, although not exclusively, white light emitting devices based on LEDs (Light Emitting Diodes) that are used to excite two or more phosphor materials that are located remote to the LED(s).
• the invention further concerns wavelength conversion components for converting the color (wavelength) of light generated by the solid-state light emitter.
• white LEDs are known in the art and are a relatively recent innovation. It was not until LEDs emitting in the blue/ultraviolet part of the electromagnetic spectrum were developed that it became practical to develop white light sources based on LEDs. As taught, for example in US 5,998,925, white LEDs include one or more phosphor materials, that is photo-luminescent materials, which absorb a portion of the radiation emitted by the LED and re-emit radiation of a different color (wavelength). Typically, the LED chip or die generates blue light and the phosphor(s) absorbs a percentage of the blue light and re- emits yellow light or a combination of green and red light, green and yellow light, green and orange or yellow and red light. The portion of the blue light generated by the LED that is not absorbed by the phosphor combined with the light emitted by the phosphor provides light which appears to the human eye as being nearly white in color.
• a mixture of phosphor materials is provided as a single layer on the light emitting surface of the LED die.
• the different phosphor materials can be provided as respective layers overlying the LED die.
• Embodiments of the invention concern solid-state light emitting devices comprising one or more solid-state light emitters, typically LEDs, that is/are operable to generate blue light which is used to excite a photo luminescence wavelength conversion component that includes at least two blue light excitable phosphor materials.
• the phosphor materials are provided as a pattern of areas in which there is little or no overlap of areas of different phosphor materials.
• the inventors have discovered that in contrast to devices in which the different phosphor materials are provided as a mixture in a single layer or provided as overlaying separate layers, minimizing any overlap of the different phosphor materials can increase the quantum efficiency of the device and improve the CRI (Color Rendering Index) of light generated by such a device.
• a light emitting device comprises at least one light emitter operable to generate blue light and a wavelength conversion component comprising at least two phosphor materials, wherein the phosphor materials are operable to absorb at least a portion of said blue light and emit light of different colors and wherein the emission product of the device comprises the combined light generated by the at least one light emitter and the phosphor materials and wherein the phosphor materials are provided as a pattern of substantially non- overlapping areas on a surface of the component.
• the phosphor material areas can be separated by a region, or gap, that does not contain phosphor material.
• the regions or gaps can be light transmissive, light reflective or light blocking.
• the gaps act as windows allowing the emission of blue and phosphor generated light from the component.
• the regions or gaps separating phosphor areas are less than an about 0.5mm (-ten thousandths of an inch or lOmil) and are typically of order 0.05mm.
• phosphor material areas can be configured to abut each other or overlap slightly.
• overlapping slightly means that the total area of overlap of phosphor material areas is much less than the total area of non-overlapping phosphor material areas.
• the area of overlap is preferably as small as possible and is typically less than 0.1% of the total area.
• the pattern of phosphor material areas can comprise both regular and irregular patterns including for example a pattern of strips or lines of different phosphor materials; a pattern of pixels that can be circular, oval, square, rectangular, triangular, hexagonal or a tiling of geometric areas for example a tiling of rectangular or square areas.
• the phosphor material areas preferably have at least one dimension that is less that about 2mm.
• the pattern of phosphor materials comprises strips or lines of alternating phosphor materials of a width less than about 5mm.
• the pattern of phosphor materials comprises a pattern of circular dots or pixels of the first phosphor material with the second phosphor material filling the area between the pixels.
• the size and/or relative areas of the phosphor materials areas can be vary over the wavelength conversion component. It is envisioned that by configuring the pattern in such a way, this can be used to reduce angular variations in the color of the emission product of the device. For example for a white light emitting device it is envisaged to provide relatively more red emitting phosphor material than yellow emitting phosphor materials on regions, often the central region, of the wavelength conversion component where the incident blue light intensity is greatest. In one example the size of the red phosphor material areas can be larger towards the center of the component and reduce in size away from the central region
• the wavelength conversion component is located advantageously located at a distance of at least 5mm from the light emitter(s) and is preferably separated there from by an air gap.
• the wavelength conversion component can be light transmissive and configured to convert the wavelength of at least a portion of the light transmitted through the component.
• the wavelength conversion component comprises a light transmissive substrate on a surface of which the pattern of phosphor materials are provided as at least one layer. Due to the isotropic nature of scattering of blue light by the phosphor materials and the isotropic nature of the photo luminescence process, a proportion of blue light and approximately half of phosphor generated light will be emitted from the wavelength conversion component back towards the light emitter. To maximize light emission from the device the back scattered blue light and phosphor converted light should be re-directed back to the wavelength conversion component for it to be transmitted through the component and to contribute to the emission product.
• the device advantageously further comprise a light reflective chamber surrounding the light emitter and wavelength conversion component that is configured to re-direct backscattered light towards the wavelength conversion component.
• the light reflective chamber can comprise a light reflective metal surface or a light reflective polymer surface.
• the light reflective surface can comprise a mirror-like (non-diffusive) or a Lambertian-like (diffusive) reflective surface.
• the wavelength conversion component can be configured to prevent phosphor converted light generated in a direction back towards the light emitter by one phosphor material being re-directed by the light reflective chamber back through an area of the other phosphor material.
• the device comprises a wavelength selective reflective filter that is configured to be reflective to at least wavelengths of light generated by the two phosphor materials and is substantially transmissive to light generated by the at least one light emitter.
• the wavelength reflective filter prevents the emission of phosphor converted light from the wavelength conversion component in a direction towards the light emitter thereby virtually eliminating inter-phosphor absorption since phosphor converted light will be reflected back into the phosphor material area that generated the light to begin with.
• the wavelength selective reflective filter comprises a respective reflective filter associated with each phosphor material area in which the reflective filter associated with the first phosphor material is configured to be reflective to at least wavelengths of light generated by the first phosphor material and is substantially transmissive to light generated by the at least one light emitter and in which the reflective filter associated with the second phosphor material is configured to be reflective to at least wavelengths of light generated by the second phosphor material and is substantially transmissive to light generated by the at least one light emitter.
• the wavelength selective filter is preferably located between the light transmissive substrate and phosphor material areas.
• the wavelength selective filter can be provided on a face of the light transmissive substrate and the pattern of phosphor material areas then deposited on the wavelength selective filter.
• the wavelength selective filter can comprise a multilayer structure comprising for example multiple layers of dielectric materials or a grating type structure.
• the pattern of phosphor materials is provided on the substrate by screen printing.
• the pattern of phosphor material can be applied to the substrate using other deposition techniques including inkjet, letterpress, gravure or flexograph printing.
• the light transmissive substrate can comprise a light transmissive polymer such as an acrylic, a polycarbonate, an epoxy or a silicone or a glass.
• the wavelength conversion component can be light reflective and configured to convert the wavelength of at least a portion of the light reflected by the component.
• One such wavelength conversion component comprises a light reflective surface on which the pattern of phosphor materials is provided as at least one layer.
• the pattern of phosphor materials can be provided on the light reflective substrate by for example printing, screen printing or inkjet printing.
• the light reflective surface has as high a reflectance as possible and is preferably at least 0.9.
• the light reflective surface can comprise a light reflective metal such as for example silver, aluminum or chromium. Alternatively it can comprise a light reflective polymer, a light reflective paper or a light reflective paint.
• the at least one light emitter comprises a solid-state light emitter such as an LED that is operable to generate blue light having a peak wavelength in a wavelength range 380nm to 480nm and typically about 440nm to 450nm.
• a solid-state light emitter such as an LED that is operable to generate blue light having a peak wavelength in a wavelength range 380nm to 480nm and typically about 440nm to 450nm.
• a wavelength conversion component for a solid-state light emitting device for converting the wavelength of at least a portion of light generated by a light emitter comprises on a surface thereof a pattern of at least two phosphor materials configured as a pattern of substantially non-overlapping areas.
• neighboring phosphor material areas can be separated by a region, or gap, that does not contain phosphor material.
• the regions or gaps separating neighboring phosphor areas are less than an 0.5mm (—0.01 inch) and can typically be or order 0.05mm (0.001 inch or lOmil).
• neighboring phosphor material areas can abut each other.
• the phosphor material areas preferably have at least one dimension that is less that about 5mm.
• the wavelength conversion component is light transmissive and comprises a light transmissive substrate on which the pattern of phosphor materials are provided as at least one layer.
• the wavelength conversion component can further comprise a wavelength selective reflective filter that is configured to be reflective to at least wavelengths of light generated by the two phosphor materials and is substantially transmissive to wavelengths of light generated by the light emitter.
• the wavelength selective reflective filter comprises a respective reflective filter associated with each phosphor material in which the reflective filter associated with a first phosphor material is configured to be reflective to at least wavelengths of light generated by the first phosphor material and is substantially transmissive to wavelengths of light generated by the light emitter and in which the reflective filter associated with the second phosphor material is configured to be reflective to at least wavelengths of light generated by the second phosphor material and is substantially transmissive to wavelengths of light generated by the light emitter.
• the wavelength selective filter can be located between the light transmissive substrate and phosphor material areas.
• the wavelength selective filter can comprise a multilayer dielectric mirror or a grating type structure.
• the light transmissive substrate can comprise an acrylic, a polycarbonate, an epoxy, a silicone or a glass.
• the wavelength conversion component is light reflective and comprises a light reflective surface on which the pattern of phosphor materials are provided as at least one layer.
• the light reflective surface is highly reflective and has a reflectance of at least 0.9.
• the light reflective surface can comprise a reflective metal such as silver, aluminum or chromium, a light reflective polymer, a light reflective paper or a light reflective paint.
• the pattern of phosphor materials is provided on wavelength conversion component by printing, screen printing, inkjet printing or other deposition techniques.
• the phosphor materials preferably comprise an inorganic material such as for example an orthosilicate, nitride, sulfate, oxy-nitride, oxy-sulfate or garnet (YAG) material has a particle size in a range 2 ⁇ to 60 ⁇ and more particularly ⁇ to 20 ⁇ .
• an orthosilicate, nitride, sulfate, oxy-nitride, oxy-sulfate or garnet (YAG) material has a particle size in a range 2 ⁇ to 60 ⁇ and more particularly ⁇ to 20 ⁇ .
• FIG. 1 is schematic representation of an LED-based light emitting device in accordance with an embodiment of the invention
• FIG. 2 are schematic plan and side views of a photoluminescence wavelength conversion component for use in the light emitting device of FIG. 1;
• FIG. 3 are schematic plan and side views of another photoluminescence wavelength conversion component for use in the light emitting device of FIG. 1;
• FIG. 4 is a schematic plan view of a further photoluminescence wavelength conversion component for use in the light emitting device of FIG. 1
• FIGS. 5(a) to 5(d) are schematic representations illustrating a method of fabricating a photoluminescence wavelength conversion component
• FIG. 6 is a schematic illustrating the principle of operation of a known light emitting device
• FIG. 7 is a schematic illustrating the principle of operation of the light emitting device of FIG. 1;
• FIG. 8 is a plot of relative intensity versus wavelength for (a) a light emitting device in accordance with the invention and (b) the known light emitting device of FIG. 6;
• FIG. 9 is a schematic of a photoluminescence wavelength conversion component in accordance with yet another embodiment of the invention for use in the light emitting device of FIG. 1;
• FIG. 10 is a schematic of a photoluminescence wavelength conversion component in accordance with yet a further embodiment of the invention for use in the light emitting device of FIG. 1
• FIG. 11 is a schematic representation of an LED-based light emitting device in accordance with a further embodiment of the invention.
• FIG. 12 is a schematic illustrating the principle of operation of the light emitting device of FIG. 11.
• FIG. 13 is a schematic of a photoluminescence wavelength conversion component in accordance with another embodiment of the invention for use in the light emitting device of FIG. 11.
• Embodiments of the invention are directed to light emitting devices comprising one or more solid-state light emitters, typically LEDs, which is/are operable to generate blue light which is used to excite a photoluminescence wavelength conversion component that includes at least two blue light excitable phosphor materials.
• the phosphor materials are preferably provided on the surface of the wavelength conversion component as a pattern of substantially non- overlapping regions which the inventors have found can give an improved quantum efficiency and CRI. It is believed that the improved quantum efficiency results from a reduction of light of a shorter wavelength (higher energy) generated by one phosphor material being absorbed by the other phosphor material.
• like reference numerals are used to denote like parts.
• FIG. 1 shows a schematic representation of an LED-based white light emitting device 10 in accordance with an embodiment of the invention.
• the device 10 comprises a blue light emitting LED 12 and a photoluminescence wavelength conversion component 14 located remotely to the LED.
• the wavelength conversion component 14 can comprise a light transmissive substrate (window) 16 having on one face a pattern of at least two phosphor materials 18, 20.
• the light transmissive window 16 can comprise any light transmissive material such as a polymer material for example a polycarbonate, acrylic, silicone or epoxy or a glass such as a quartz glass.
• the light transmissive window 16 is planar, often a circular disc, though it can be square, rectangular or other shapes depending on the intended application.
• the diameter can typically be between about 1cm and about 15cm that is an aperture of area 0.8 cm 2 and 180cm 2 .
• the light transmissive window 16 comprise an optical component that directs light in a selected direction such as a convex, concave or Fresnel lens.
• the wavelength conversion component is preferably located remote to the LED, that is, physically separated by a distance of at least 5mm. Typically the wavelength conversion component is separated from the LED by an air gap.
• the blue LED 12 can comprise a GaN-based (gallium nitride-based) LED that is operable to generate blue light 22 having a peak wavelength ⁇ in a wavelength range 380nm to 480nm (typically 440nm to 450nm).
• the blue LED 12 is configured to irradiate the wavelength conversion component 14 with blue light 22 whereat a proportion is absorbed by the phosphor materials 18, 20 which in response emit light 24, 26 of a different respective wavelength ⁇ 2 , ⁇ 3 , typically red and yellow light for a warm white light emitting device.
• the emission product 28 of the device 10 which is configured to appear white in color comprises the combined light 22 emitted by the LED and the light 24, 26 generated by each of the phosphor materials 18, 20.
• the device can further a light reflective chamber 30 surrounding the LED 12 and wavelength conversion component 14 to re-direct backscattered light towards the wavelength conversion component 14.
• the light reflective chamber is configured to direct light 22 generated by the LED 12 that is backscattered by the wavelength conversion component 14 and phosphor generated (photoluminescence) light 26, 28 generated by the phosphor materials.
• FIG. 2 shows schematic plan and side views of a photoluminescence wavelength conversion component 14 in accordance with an embodiment of the invention.
• the phosphor materials 18, 20 are configured as a pattern of areas comprising a series of parallel non-overlapping alternating strips or lines of width Wi and w 2 respectively.
• Each phosphor material strip comprises a uniform thickness layer of phosphor material of a respective thickness ti, t 2 . It will be appreciated that the thickness of the phosphor material will determine the color of the light generated by the phosphor area.
• phosphor material areas 20 comprising green or yellow light emitting materials have a thickness t 2 than is greater than phosphor material areas 18 comprising red light emitting phosphor materials of thickness ti.
• t 2 is approximately one and a half times ti.
• the strips of different phosphor materials can be separated a narrow gap 30 of width W3.
• the gaps 30 prevent overlapping of the phosphor areas occurring during printing.
• the gaps 30 also allow the transmission of a proportion of the LED generated light 22.
• the gaps 30 between different phosphor material areas can comprise a physical space though in other embodiments the gap can comprise a region such as a light transmissive medium that does not contain any phosphor material.
• An example of a wavelength conversion component 14 for generating warm white (CCT-3000K) comprises a 2.5 inch (64mm) diameter circular light transmissive disc with a pattern of alternating strips of a red light ( ⁇ 2 peak wavelength ⁇ 630nm) emitting nitride phosphor material 18 and yellow light ( ⁇ 3 peak wavelength ⁇ 550nm) emitting YAG material 20.
• the phosphor material areas have a thickness ⁇ 60 ⁇ and ⁇ ; 2 ⁇ 100 ⁇ .
• the weight loading of phosphor material to light transmissive binder (Star Technology U.V. cure acrylic adhesive UVA4103) is approximately 1.2: 1 and 2.8: 1 for the red nitride and yellow YAG phosphor materials respectively.
• the pattern is configured such that the red and yellow phosphor materials respectively cover -44% and -56% of the surface area (aperture) of the wavelength conversion component.
• the strips are as narrow as possible and typically have a width that is less that about 2mm.
• the phosphor areas can be configured to abut each other.
• FIG. 3 shows schematic plan and side views of a wavelength conversion component 14 in accordance with another embodiment of the invention.
• the phosphor materials 18, 20 are configured as a pattern comprising an array of rectangular areas of width w and length 1 ⁇ , 1 2 respectively. As shown the rectangular areas can be separated by a narrow gap 30 of width W3.
• the color of the emission product 28 generated by such a component 14 can be selected by the ratio of the areas Ai, A 2 of the different phosphor material areas that is ⁇ : ⁇ 2 (li.w:l 2 .w).
• the color of light generated by the each phosphor material area will also depend on the thickness ti, t 2 of the areas.
• the phosphor material areas typically have at least one dimension that is less that about 2mm (w ⁇ 2mm and/or ((li, 1 2 ) ⁇ 2mm).
• FIG. 4 is schematic plan view of a wavelength conversion component 14 in accordance with a further embodiment of the invention.
• the pattern of phosphor materials is configured as a square array of circular areas, or dots, of the first phosphor material 18 with the second phosphor material 20 filling between circular areas.
• a narrow gap 30 of width W3 can be provided between each of the circular phosphor areas 18 and the surrounding phosphor material.
• the circular phosphor material areas 18 typically have a diameter ⁇ that is less that about 2mm and a maximum separation s between circular areas that is less that about 2mm.
• the various patterns of phosphor materials described are exemplary only and that other patterns are within the scope of the invention.
• the pattern of phosphor materials can comprise regular or irregular patterns of circular, oval, square, triangular, diamond or hexagonal phosphor areas.
• the phosphor materials 18, 20, which are in powder form, are thoroughly mixed in known proportions with a light transmissive binder material 32 such as a polymer material (for example a thermally or U.V. curable silicone, acrylic or an epoxy material) such as Star Technology's U.V. curable acrylic adhesive UVA4103 or a clear ink such as for example Nazdar's® U.V. curable litho clear overprint PSLC-294.
• the phosphor/binder mixture is applied to the face of the window 16 as one or more layers of uniform thickness. In a preferred embodiment the mixture is applied to the light transmissive window by screen printing and the thickness t of the layer controlled by the screen mesh size and the number of printing passes.
• FIG. 5(a) to 5(d) are schematic representations illustrating an example of a method of fabricating a wavelength conversion component.
• the phosphor areas 20 are screen printed using a first screen.
• the screen is changed and the other phosphor areas 18 are then printed in between the phosphor areas 20 using a second screen (FIG. 5(b)).
• the first screen is then used to print a further layer of the phosphor areas 20 overlying the first (FIG. 5(c)).
• the second screen is used to print a further layer of the phosphor areas 18 overlying the first (FIG. 5(d)).
• t the required thickness of the phosphor areas will determine the number of print passes.
• the phosphor mixture can be applied using other printing methods such as inkjet, letterpress, gravure or flexograph printing as well as other deposition techniques.
• the phosphor material can comprise an inorganic or organic phosphor such as for example silicate-based phosphor of a general composition A 3 Si(0,D) 5 or A 2 Si(0,D) 4 in which Si is silicon, O is oxygen, A comprises strontium (Sr), barium (Ba), magnesium (Mg) or calcium (Ca) and D comprises chlorine (CI), fluorine (F), nitrogen (N) or sulfur (S).
• silicate-based phosphor of a general composition A 3 Si(0,D) 5 or A 2 Si(0,D) 4 in which Si is silicon, O is oxygen, A comprises strontium (Sr), barium (Ba), magnesium (Mg) or calcium (Ca) and D comprises chlorine (CI), fluorine (F), nitrogen (N) or sulfur (S).
• silicate-based phosphors are disclosed in United States patents US 7,575,697 "Europium activated silicate-based green phosphor” (assigned to Intematix Corp.), US 7,601,276 “Two phase silicate-based yellow phosphor” (assigned to Intematix Corp.), US 7,601,276 “Silicate- based orange phosphor” (assigned to Intematix Corp.) and US 7,311,858 "Silicate-based yellow- green phosphor” (assigned to Intematix Corp.).
• the phosphor can also comprise an aluminate- based material such as is taught in our co-pending patent application US2006/0158090 "Aluminate -based green phosphor” and patent US 7,390,437 "Aluminate -based blue phosphor” (assigned to Intematix Corp.), an aluminum-silicate phosphor as taught in co-pending application US2008/0111472 "Aluminum-silicate orange-red phosphor” or a nitride-based red phosphor material such as is taught in our co-pending United States patent application 12/632,550 filed December 7, 2009.
• the phosphor material is not limited to the examples described herein and can comprise any phosphor material including nitride and/or sulfate phosphor materials, oxy-nitrides and oxy- sulfate phosphors or garnet materials (YAG).
• the phosphor material comprises particles with a particle size ⁇ to 20 ⁇ and typically of order 15 ⁇ .
• the phosphor material can comprise particles of a size 2 ⁇ to 60 ⁇ depending on the deposition technique used to pattern them.
• FIG. 6 shows a schematic of a LED- based light emitting device in which the wavelength conversion component 14 includes a mixture of the two phosphor material 18, 20 in a single layer.
• blue light 22 of wavelength ⁇ from the LED 12 is transmitted by the light transmissive binder 32 until it strikes a particle of phosphor material. It is believed that on average as little as 1 in 1000 interactions of a photon with a phosphor material particle results in absorption and generation of photoluminescence light. The majority, of order 99.9%, of interactions of photons with a phosphor particle result in scattering of the photon.
• the amount of phosphor material is typically selected to allow approximately 5% of the total incident blue light to be emitted from the window and contribute to the emission product.
• the device is configured such that the majority, approximately 85%, of the incident light is 22 absorbed by the phosphor material and re-emitted as photoluminescence light 24, 26. Due to the isotropic nature of photoluminescence, approximately half of the light 24, 26 generated by the phosphor material will be emitted in a direction towards the LED.
• the inventors have appreciated that as well as photoluminescence light generated by the phosphor materials 18, 20 absorbing the higher energy (shorter wavelength) light 22 from the LED (that is the conversion of blue light 22 ( ⁇ ) to yellow light 26 ( ⁇ 3 ) and red light 24 ( ⁇ 2 )), the longer wavelength ( ⁇ 2 ) emitting phosphor material 18 can also be excited by absorbing the higher energy (shorter wavelength) light ( ⁇ 3 ) generated by the other phosphor material 20. This inter-phosphor absorption results in a proportion 34 of the yellow light 26 being converted to red light 24 ( ⁇ 3 ⁇ 2 ). Since the photoluminescence process always results in an energy loss (Stokes loss) this additional wavelength conversion results in an energy loss and a reduction in quantum efficiency.
• FIG. 7 is a schematic illustrating operation of the device of FIG. 1.
• the operation of the device of the invention is similar to that of FIG. 6 but due to the physical separation of the two phosphor materials 18, 20 into respective areas this virtually eliminate inter-phosphor absorption between immediately adjacent phosphor material areas.
• approximately half of the phosphor generated light 24, 26 will be emitted from the phosphor wavelength conversion component 14 in a direction towards the LED 12 and then re-directed back towards the wavelength conversion component 14 by the light reflective chamber 30.
• FIG. 8 shows measured emission spectra (intensity versus wavelength) 38, 40 for (a) a light emitting device in accordance with the invention with a pattern of phosphor materials and (b) a light emitting device with a mixture of the same phosphor materials. Both devices are designed to generate warm white light (CCT-3000K) with a target color CLE. (0.437, 0.404).
• the wavelength conversion component comprises a 2.5 inch diameter polycarbonate disc (20mil Lexan® 8010) with the phosphor materials provided on one face.
• the phosphor materials comprise a pattern of alternating strips (FIG.
• the phosphor material are mixed in weight proportions 87.8% yellow phosphor material to 12.2% red phosphor material and the phosphor material mixture screen printed on the polycarbonate disc.
• Locating the phosphor material remote to the LED provides a number of benefits namely reduced thermal degradation of the phosphor material. Additionally compared with devices in which the phosphor material is provided in direct contact with the light emitting surface of the LED die, providing the phosphor material remotely reduces absorption of backscattered light by the LED die. Furthermore locating the phosphor remotely enables generation of light of a more consistent color and/or CCT since the phosphor material is provided over a much greater area as compared to applying the phosphor directly to the light emitting surface of the LED die with its areas that is typically at least an order of magnitude smaller.
• the reflective filter 42 can comprise a multilayered filter structure such as for example a dichroic mirror or a mirror grating that is configured to have a reflection waveband that reflects light including light of at least wavelengths ⁇ 2 , ⁇ 3 generated by the phosphor materials 18, 20 whilst allowing the transmission of light of wavelength ⁇ generated by the LED 12.
• the gaps 30 between phosphor regions can be filled with a light reflective or light blocking material 44.
• the reflective filter 42 prevents the emission of phosphor converted light 24, 26 from the wavelength conversion component in a direction towards the LED thereby virtually eliminating inter-phosphor absorption since phosphor converted light will be reflected back into the phosphor material area that generated the light to begin with.
• the light reflective or light blocking regions 44 between phosphor material areas can eliminate inter-phosphor absorption occurring in regions of the phosphor material areas that are immediately adjacent with a neighboring phosphor material area.
• the material 44 can comprise a screen printable ink, for example a light reflective ink, which can be printed as a part of the printing process of the phosphor material areas.
• it can comprise a light reflective metal that can be used to define recesses for receiving a respective phosphor material.
• FIG. 10 shows a further light transmissive wavelength conversion component 14 in which each phosphor material area 18, 20 overlays a respective wavelength selective reflective filter area 42a, 42b.
• the light reflective filters areas 42a are configured to have a reflection waveband that reflects light of at least wavelength ⁇ 2 generated by the phosphor material 18 whilst allowing the transmission of light of wavelength ⁇ generated by the LED 12.
• the light reflective filters areas 42b are configured to have a reflection characteristic that reflects light at least wavelength ⁇ 3 generated by the phosphor material 20 whilst allowing the transmission of light of wavelength ⁇ generated by the LED 12.
• a benefit of providing a respective reflective filter 42a, 42b for each phosphor material areas is that each filter can have a narrower reflection waveband making them easier to fabricate.
• FIG. 11 shows a schematic representation of an LED-based white light emitting device 10 in accordance with a further embodiment of the invention.
• the wavelength conversion component 14 is light reflective and comprises a light reflective surface 46 on which the pattern of phosphor materials 18, 20 is applied.
• the light refiective surface 46 can comprise a paraboloidal surface though it can comprise any surface including planar, convex and concave surfaces.
• the light reflective surface is as reflective as possible and preferably has a reflectance of at least 0.9.
• the light reflective surface can comprise a polished metallic surface such as silver, aluminum, chromium; a light reflective polymer, a light reflective paper or a light refiective paint.
• the light refiective surface is preferably thermally conductive.
• FIG. 12 Operation of the light emitting device of FIG. 11 is illustrated in FIG. 12 and is not described in detail as it is similar to that of FIG. 7.
• the thickness of the phosphor conversion layer 18, 20 can be of up to half, i.e. t/2, compared to arrangements with a light transmissive wavelength conversion component (FIG. 1).
• FOG. 1 light transmissive wavelength conversion component
• FIG. 13 is a schematic of a further light reflective wavelength conversion component in accordance with the invention.
• the gaps 30 between phosphor regions are filled with a light transmissive or light blocking material 44.

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• 2010
  • 2010-09-28 US US12/892,754 patent/US8354784B2/en not_active Expired - Fee Related
• 2011
  • 2011-09-20 EP EP11831192.7A patent/EP2622939A4/de not_active Withdrawn
  • 2011-09-20 KR KR1020137007970A patent/KR20130122733A/ko not_active Application Discontinuation
  • 2011-09-20 CN CN2011800469305A patent/CN103155700A/zh active Pending
  • 2011-09-20 JP JP2013530233A patent/JP2013538011A/ja not_active Withdrawn
  • 2011-09-20 WO PCT/US2011/052382 patent/WO2012047505A1/en active Application Filing
  • 2011-09-28 TW TW100135072A patent/TW201251136A/zh unknown

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